Computer-related electronic systems are commonly constructed using multiple interconnected circuit boards. The largest of these circuit boards is typically called the motherboard. Ancillary circuit boards such as CPU cards, memory cards and input/output cards are typically called daughterboards. Sockets are provided on the motherboard for receiving one or more daughterboards and making appropriate electrical connections between components mounted on the daughterboards and those mounted on the motherboard. Such sockets are usually designed so that the daughterboards may be easily removed and replaced.
Special thermal management problems are presented by motherboard/daughterboard systems wherein high heat dissipation components are mounted on the daughterboards. Specifically, it has been found that fan-driven heat sinks are necessary to prevent the high heat dissipation components such as CPU chips on the daughterboards from overheating.
One example of such a motherboard/daughterboard system is described in the single edge contact cartridge ("SECC") packaging specifications promulgated by Intel Corporation. Referring now to FIG. 1, the packaging specification for boxed SECC2 processors describes a daughterboard 100 on which a CPU is mounted. Daughterboard 100 is adapted to engage a socket 102 on a motherboard 104 so that daughterboard 100 is oriented substantially perpendicular to motherboard 104. A heatsink 106 is disposed on one side of daughterboard 100 between the CPU and a fan 108. On the opposite side of daughterboard 100, an SECC2 cover plate 110 is provided to help anchor heatsink 106 to daughterboard 100. Heatsink 106 is generally rectangular and includes plural elongate fins 112. Each of fins 112 lies on a plane that is substantially parallel to motherboard 104. The axis of rotation of fan 108 is also substantially parallel to motherboard 104. A fan shroud 114 is provided to direct air flow through heatsink 106 from the ends of fins 110 to the middle of fins 110 under fan 108 as shown in FIG. 2.
Heatsink 106 also includes tabs 116 on either end. (Tabs 116 are best illustrated in FIG. 3.) Each of tabs 116 defines a notch 118 for engaging a retaining member of socket 102. An example of such a retaining member is universal retention mechanism 400 ("URM") shown in FIG. 4. URM 400 includes a frame with top surfaces 406 and a resilient arm 402. Resilient arm 402 includes retaining ledges 404. Typically, one URM 400 is disposed on each end of socket 102 with its retaining ledges 404 facing inward toward the socket. When daughterboard 100 is pushed into socket 102, notches 118 on either side of heatsink 106 engage the underside of ledges 404, thereby helping to retain daughterboard 100 in socket 102.
A number of disadvantages are associated with prior art motherboard/daughterboard systems such as those illustrated in FIGS. 1-3. For example, it is frequently necessary to place multiple daughterboards in parallel rows on the same motherboard. Because each prior art daughterboard has a heatsink 106, a shroud 114 and a fan 108 stacked in a direction perpendicular to the plane of the daughterboard, multiple prior art daughterboards require a large amount of motherboard area. Moreover, systems that require multiple prior art daughterboards are expensive and noisy because each daughterboard in the system includes a noiseproducing and relatively expensive fan 108.
It is therefore an object of the invention to provide a daughterboard system that conserves motherboard area when it is necessary to mount more than one daughterboard on the motherboard.
It is a further object to provide such a daughterboard system so that high heat dissipation components such as CPU chips can be mounted on the daughterboard.
It is a still further object to make the daughterboard system less expensive and less noisy than the daughterboard systems of the prior art.